This invention relates to a method for detecting a particle agglutination reaction with the aid of a flow cell type reaction vessel.
Various methods have been proposed for detecting a particle agglutination reaction in order to identify various kinds of blood types and the existence or non-existence of various kinds of antigens and antibodies.
In one known method, winecup-shaped reaction vessels are used and in another known method a plate having a number of reaction vessels with conical bottoms is used. These known methods may be classified as a batch system in which successive samples and a reagent are delivered into respective reaction vessels to form test liquids therein. There has been also developed an agglutination reaction detecting method of a flow cell type in which successive test liquids are supplied to a flow cell. One of the known examples of such an agglutination reaction detecting apparatus will be further explained in detail with reference to FIG. 1.
In FIG. 1, the apparatus comprises a coiled tube 1, a tube assembly 2 including branch tubes 2a, 2b, 2c and 2d, a light source 3 and a light receiving element 4 arranged on both sides of the branch tube 2d. It should be noted that at least the branch tube 2d is made of transparent material. Successive test liquids T.sub.1, T.sub.2 . . . containing particles such as blood cells are supplied into the coiled tube 1 with air bubbles A.sub.1, A.sub.2 . . . interposed between successive test liquids. In this manner, the test liquids can be supplied to the tube assembly 2 without causing contamination between successive test liquids. While the test liquid is passed through the coiled tube 1, the agglutination reaction proceeds. If the agglutination reaction occurs, the particles are agglutinated and the thus agglutinated particles descend quickly into the branch tubes 2a and 2b. Therefore, the test liquid fed into the branch tube 2d which serves as a measuring chamber contains a smaller amount of particles. Contrary to this, when there is no agglutination reaction, the test liquid supplied into the branch tube 2d contains a greater amount of particles, because the amount of particles which descend into the branch tubes 2a and 2b is smaller. Therefore, by measuring the transmittivity or absorbance of the test liquid in the branch tube 2d by means of the light source 3 and light receiving element 4, it is possible to detect whether the agglutination reaction has occurred or not. That is to say, when the agglutination reaction occurs, the transmittivity becomes larger, whilst in case of non-agglutination reaction, in transmittivity becomes smaller.
However, in the known apparatus shown in FIG. 1, the detection of the agglutination reaction could not be effected in the coiled tube 1 serving as a reaction chamber and it is necessary to provide the measuring tube assembly 2 separately from the reaction vessel 1. Therefore, the construction becomes complicated and very large. Further, if the agglutination reaction is weak, large masses of particles are not formed and thus, the descending speed is slow, so that the amount of the particles descending into the branch tubes 2a and 2b is small. Therefore, it is difficult to differentiate the weak agglutination reaction from non-agglutination reaction. Moreover, the measured results might be subjected to variation or fluctuation in the density of particles in the test liquids, i.e. errors in amounts of delivered samples and reagents. Due to the above problems, it is difficult to detect precisely the agglutination reaction by means of the known apparatus. It should be further noted that since the known apparatus does not directly detect the agglutinated particles per se, its detection accuracy is inherently low.